With the beginning of autumn almost all succulent and cacti begin to prepare for the vegetative stasis which will last until February/March. In the winter months, cacti (with some exceptions such as Melocactus, Discocactus and epiphytes such as Epiphyllum) and many succulents (with the exception of those originating from the southern hemisphere or areas such as Madagascar) stop growth and go dormant to recover energies and be able to flourish during the following season. In these months the plants should be kept cold and should not be watered. However, it is useful to carry out some preventive treatments to prevent the formation of mold or fungi during these months, thanks to the winter humidity, which, when the temperature start to rise, triggers rot. Warning: preventive treatments with chemical products can be useful but do not necessarily have to be carried out. It is simply a preventive measure, since the best form of defense is always the spartan cultivation of plants accompanied by a good exchange of air during autumn and winter. There are growers who limit these treatments to the essentials, perhaps favoring products with a low environmental impact (I myself have adopted this decision for years) and growers who abuse chemical products in the hope of thus making their plants invulnerable to animal parasites, fungi and mold.

In this article, which completes what has already been explained in other articles (which you will find thanks to the internal links) we see what is advisable to do in these weeks to protect the plants and limit losses due to rot or parasites as much as possible. (…)

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L'articolo Here comes autumn: what treatments can we do to protect succulents and reduce losses? proviene da Il fiore tra le spine.

We see them in detail in the following article (…).

Premise

By the time of June, two first dangers for succulent plants should have passed by now, if we have done everything correctly (and regardless of the fact that this spring has been quite anomalous). I am referring to the danger of cracks on the cacti stems and that of burns following a late or “hasty” exposure. Once the cacti have resumed vegetating after the winter stasis, in fact, it may happen that following the first waterings (if too abundant or too close together) the stem “splits”. In this period of the year, even in the case of a wet and cold spring like the latter, cacti and succulents should have already received at least two or three waterings and the stems of the plants should have swollen. If the recovery has taken place gradually and the plants have returned swollen, the risk of stem splitting for this year can be said to have been archived.

In some ways similar speech in terms of exposure: to date all the plants should have been in their ideal location for some time now, where they will remain until autumn. In other words, those who kept cacti and succulents in the basement, entrance halls or garages should have moved the plants to full light (or half light depending on the genre) by now, under penalty of etiolation. Abruptly moving the plants now, with the June sun starting to get stronger, can expose the plants to the risk of severe burns on the stems. Whether the spring is cool or not, whether it is humid or not, the plants must be gradually accustomed to intense sun or direct sun and this must be done between the end of March and the beginning of April. In this way cacti and succulents are able to get used to direct sunlight very gradually, strengthening the epidermis well before the summer sun hits them. If you haven’t moved your plants yet, do it immediately but repair them with shading nets (especially during the hottest hours of the day), otherwise the first burns will begin to appear in the coming weeks!

Maximum air

Having exhausted the necessary premises, which are nothing if not common practices in the correct cultivation of cacti and succulents in general, we recall that the main element of cultivation, at this point, is trivially… the air. Trivially, because this element is often underestimated, or even not considered at all, taking it for granted. The air, on the other hand, is the main factor for the healthy growth of any plant and in this season, with temperatures starting to rise significantly (on sunny days in a completely open greenhouse it can easily exceed 40 degrees Celsius already in June, let alone August), the plants need as much air circulation as possible.

Anyone who cultivates in a very large professional greenhouse will have to open the structure as much as possible, raising the side curtains and possibly leaving the front and rear doors open. Those who cultivate on balconies and terraces should have no problems whatsoever, while those who cultivate in those small greenhouses covered with a transparent cloth must do nothing but… get rid of the greenhouses, remove all the plants from there and disassemble the greenhouses, which can return comfortable, at best, in winter (although they are still not the best due to the limited air circulation they allow). In this period, if we keep the plants in this type of structure, even by raising the openings in the transparent sheet to the maximum, we will still not be able to ensure the plants the air they need, and with high temperatures and humidity the risk of “boiling” plants or creating the ideal environment for the formation of molds and fungi is very high. Therefore, if you haven’t already done so, remove the greenhouses (which can be simply used as shelves) and, since the plants will not be sufficiently accustomed to the intense sun, shield them with a not too light shading net.

The importance of air and light for succulents plants.

Watering and aestivation

In this period, even if the temperatures are not yet very high this year, it is advisable to increase the frequency of irrigation. If the days are sunny and the weather does not predict rain for the following days, it can be watered once a week. The pace can also be increased to two waterings per week for some species or succulent leafy plants if slight wrinkling is noted. As always, the basic rule is to water only when the substrate appears dry and, if in doubt, postpone it. Beware of the hot months, i.e. July and August, when the difference between the maximum and minimum night-time temperatures is minimal: in conditions of persistent heat, many cacti and many succulents can go into aestivation, slowing down or blocking their growth. In these periods it is better not to water at all, since the plants do not absorb water and the soil would remain moist for too long, with the risk of root rot being triggered.
A few more waterings will have to be reserved for very young plants and seedlings, which are not yet able to tolerate long periods of drought in hot conditions and, at the same time, “push” more than adult specimens.

On the phenomenon of aestivation you will find a specific article at this link.

Fertilization and treatments

In June it is still possible to fertilize succulents. A fertilization is enough, assuming that a first fertilization was given in May or April. If the plants have been repotted a few months ago it will not be necessary to add fertilizer to the water, but if we are dealing with specimens that have lived in the same soil for years, an extra fertilization can be useful to replenish the nutrients once present in the substrate. Pay attention to the product (whether it is in powder or liquid form, it matters little), which must be specific for succulent plants and therefore low in nitrogen and rich in phosphorus and potassium, in addition to microelements. During the real summer, that is in the months of July and August, the fertilizations must instead be suspended.

As for treatments, for years I have minimized the use of pesticides and I only use copper oxychloride and Neem oil. The first is a fungicide which should be administered by nebulization only in the months in which the plants are not in vegetation (in this period it should therefore be avoided). The second is a natural product, with low environmental impact, against parasites, mites and with a modest fungicidal function. Neem oil can be administered, always by nebulization, even in this period, with the foresight to act only when the sun has gone down or early in the morning, before direct light reaches the plants. Targeted fungicides and insecticides can be used in specific cases, for example in the event of an attack by the cochineal or rot that affects several plants. In these cases it is always important to isolate sick specimens from healthy ones and carry out targeted treatments every two weeks.

Here you will find a detailed article on the main adversities of succulents, with general indications on how to intervene.

Always remember that the best weapon against pests and diseases of succulents is correct cultivation, in particular a spartan cultivation, with lots of light, lots of air, little fertilization and little fertilizing.

To repot or not to repot?

In this case there is no definitive answer: during the summer it is possible to repot. Personally I prefer to avoid – except in cases in which the intervention cannot be deferred as the plant is in evident state of suffering and has probably lost its roots – and to postpone repotting until the end of winter and spring. With new purchases, especially if the plants are in peat, repotting is instead recommended at any time of the year: it is better to stress the plant a little rather than leave it in an unsuitable substrate, running the risk of triggering rot. As always, if you repot and clean or shorten the roots, it is important to leave the flared plant in a shady place for at least ten days before repotting. After repotting, wait another week or two before watering, so as to give the roots time to heal effectively. This precaution is especially important in spring and summer, when the plants are growing and are watered regularly: obviously in winter the problem does not arise, since many succulents and almost all cacti must be kept in dry soil.

Other practices

Otherwise, summer is a relatively quiet time for the cactus and succulent grower. It is sufficient to observe the specimens and understand whether they are slowing down their growth (aestivation) or not and adjust accordingly with watering. Finally, a little maintenance certainly doesn’t hurt: you can cut the now dry floral stems in the case of plants such as Aloe, Echeveria, Crassulaceae, etc., just as it is a good thing to remove the dried flowers of the cacti, which with watering they soak in water and can feed molds and fungi.

Seasonal cures in detail

If you want a complete picture of seasonal care, with everything you need to do in spring, summer, autumn and winter to take care of cacti and succulents in the best possible way, you can consult this summary article.

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Correlated articles

Watering cacti and succulents: when and how
How to repot cacti and succulent plants
Substrates for cacti and succulents
The correct soil: the materials you can use

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L'articolo Towards summer: useful tips for taking care of cacti and succulents and avoiding nasty surprises proviene da Il fiore tra le spine.

A spring that is struggling to establish itself, temperatures that fluctuate continuously with sunny and very hot days and gloomy days with the thermometer plummeting. Above all, heavy rain almost every day for at least a week, at least here in the North Italy. Many of us have already moved their cacti and succulents outside, or have removed the winter protections (non-woven fabric or transparent sheets). Many are worried, some run for cover by bringing the plants indoors, others are undecided about what to do… Is it really the case to worry about the combination of low temperatures and persistent rain?

In this article, here are some reflections and the answer to the question that many of you are asking me these days, as always based on what I have learned in years of cultivation (…).

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L'articolo The cacti, the spring that doesn’t come and the rain that doesn’t stop: should we be worried? proviene da Il fiore tra le spine.

Let’s talk about cacti and diseases starting from a simple photo. The plant that inspired this article, and which you see above, is (or rather, was) an Ancistrocactus (=Glandulicactus) mathssonii. I had obtained this specimen with my sowing about ten years ago and fortunately eight or nine other “brothers” of this plant are still in perfect health, growing and flowering regularly. This particular plant, although treated exactly like the other specimens of that sowing and planted in the same type of substrate in which my other mathssonii live (clay, marl and 60% aggregates), a couple of years ago took a fungal pathology and within a few weeks it was dead. I think it was fusarium, but today it doesn’t matter, because the disease has run its course and what remains is… the armor of this cactus, that is a beautiful interweaving of thorns that embraces the void left by the stem which, over time, it dried up until it decomposed and disappeared altogether. The observation of what remains of this plant, which for a couple of years I have kept along a low wall not far from the greenhouse, where I usually move the diseased plants (by diseases, in this case, I mean generically pathogens and parasites) to prevent them from infecting other specimens, led me to some considerations on the cultivation and treatment of plant diseases.

Considerations that I have condensed in the following article an excerpt of which was also published in the British Cactus and Succulent Society newsletter. (…)

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L'articolo Cacti and diseases: stop anxiety, sometimes we can’t help but let Nature take its course proviene da Il fiore tra le spine.

Now let’s see everything we can do at this time of the year, especially if we don’t have a greenhouse and we grow on the windowsill, on the balcony, on a terrace or in the garden. With a warning: whatever you have to do, with succulents and cacti, you must not be in a hurry: hurry to water, hurry to treat, hurry to move the plants… Getting caught up in the rush, the anxiety, the fear of doing something wrong, is the best way to run into mistakes. So let’s see how to avoid them. (…)

Check the plants

The first fundamental action in spring is to check the plant carefully for detecting any traces of bacterial diseases (dark spots caused by fungi) or parasites (particularly the mealybug/cochineal). In the first half of mid-March, even with healthy plants, it’s however advisable to carry out some preventive treatment by spraying stems and leaves with a specific pesticide (against mealybug and spider mite) and, about ten days later, with a broad-spectrum fungicide (attention: copper oxychloride should be used only when the plants are in stasis, so from March should be suspended). Both treatments – pesticide and antibacterial – must be repeated a fortnight after to ensure complete coverage of the plants.

Give as much air as possible

When the minimum temperatures have settled at 10/12 degrees, it’s essential to give succulents as much air as possible. Plants that have overwintered indoors (except for some species, a thing to avoid!) or in cold but closed environments such as a basement, a garage or a veranda should be moved outdoors and placed on windowsills, terraces, balconies. If plants have been overwintered outdoors, protected by sheets or layers of non-woven fabric, they should simply be uncovered so they can benefit from all the possible air. In these cases, it’s necessary to pay attention to the weather because prolonged rains in a period characterized by not yet high temperatures can be dangerous for succulents, which do not tolerate water stagnation in the soil and excessive humidity. The plants must be placed on a balcony or terrace protected from the rain or covered by a roof.

The sudden changes in temperature that characterize spring, with daytime highs above twenty degrees and nighttime lows that can drop sharply below ten degrees, should not worry: in nature, almost all succulents are exposed to similar conditions and indeed greatly benefit in terms of growth and flowering. Exceptions are succulents coming from areas close to the Equator, such as those from Madagascar (Adenium obesa, but also Uncarina, Alluaudia and Pachypodium) or some cacti coming from tropical regions of South America, such as Melocactus, Discocactus, Epiphyllum, Schlumbergera, Rhipsalis: these species need minimum temperatures not lower than 15-16 degrees and to be moved outside only later, in late spring.

Air is of fundamental importance for any plant, even more so for succulents, which do not tolerate environmental humidity nor water stagnation in the substrate. In open-air, the soil dries faster, the stems can transpire effectively, and the risk of bacterial attack is significantly lowered. Tight, closed environments without air exchange are to be avoided, especially in spring and summer, when succulents are in full vegetation, and their tissues are swollen with the water that constitutes their water reserve, and it is, therefore, necessary that the soil dries quickly after the plant has absorbed the liquids it needs.

Exposure: getting plants used to it

Closely related to air is exposure to the sun. In spring (in march), it’s necessary to provide succulents with more light to encourage proper development of tissues, leaves and thorns and at the same time encourage flowering. Be careful, though: as with all plants, succulents (including Cactaceae) need to be grown gradually. Moving a plant that has spent the winter indoors outdoors and immediately placing it in full sun can be dangerous even for the most “fierce” and thorny cactus, which will suffer sunburn and stem discolouration. We will have to gradually accustom the succulents to the light, which becomes more and more intense in spring, exposing them to direct sun a little at a time. From the middle of March, it will be sufficient to place succulents on a windowsill exposed to the South or Southeast (exposure to the North is to be avoided because it does not provide enough light), or on a balcony, a terrace or directly in the garden, taking care, however, to place them in the shade of outdoor plants that will act as a screen to sunlight. Alternatively, it is possible to protect succulents with a simple gardening net or with a piece of mosquito net properly fixed to braces or supports and able to screen at least 30-40% of sun rays.

In the shade of other plants or screened by shade netting, succulents will gradually get used to direct sunlight, and within a month to a month and a half, you can bring them to the foreground or remove the shade netting. As far as exposure is concerned, it’s still important to know the needs of our succulents since there are genera that tolerate intense sun and others that prefer a little shade (like many species of Euphorbia or Haworthia, for example). When in doubt, it is good to provide succulents with bright light all day long, exposing them to direct sun rays only during the morning, not later than midday. In this way, it’s possible to avoid sunburns and to guarantee the necessary light for the best growth. Particularly for cacti, which will continue producing “important” and not stunted thorns and at the same time keep compact and harmonious stems. When we have a better knowledge of our plants and have learned their needs, we can be more “targeted” when they come to exposure and give the various specimens the right amount of direct sun (for example, in the case of almost all cacti).

To learn how to distinguish succulent plants and know their needs, you can read this article dedicated to classification.

Resume watering

As the exposure to light, which should be gradual, watering should be increased little by little. During the winter, watering should be suspended for almost all succulents, while in spring it’s necessary to accompany the resumption with initially moderate and then more sustained watering. As spring approcaches, in March (weather permitting) a couple of waterings will be enough, while in April, it will be possible to go up to one watering every ten days, making sure to wet well all the soil. From May, you can further increase the watering, reaching one per week. Be sure that between one watering and the other, the loam can dry completely. As always, the advice with succulents is not to overdo it: it’s easier for a succulent plant to die from too much water than from thirst. Consider that these plants are xerophytes, evolved to deal with long periods of drought: when in doubt, it’s a good idea to postpone watering. For regulating the frequency of watering, it’s fundamental also the composition of the soil: here, you will find the “recipes” of various substrates that I have tested over the years.

Fertilize: which products to use

With the arrival of spring and the increase in watering, it’s beneficial to fertilize (or “manure”) succulent plants to promote balanced growth and encourage flowering. As for any other plant, fertilizing is essential to replenish the soil with nutrients that are lost. However, you have to use a specific fertilizer for succulents and not rely on universal products or, worse, calibrated for other plants, such as orchids or horticultural. Wrong fertilization, both in terms of the type of product and frequency, can cause severe damage to the plant and compromise its growth, arriving, paradoxically, to weaken it, as well as deform the stem. Therefore, it’s necessary to limit fertilization (I am very stingy in this regard: two or three fertilizations per year, at most), to be administered by simple watering diluting the product in water, to a maximum of once a month from April until mid-June at the latest, with a further pass in September, before the plants slow down the vegetation.

As for the product, on the market, there are specific fertilizers for succulent plants, and generally, high-quality products have correct ratios between the various macroelements. Knowing how to interpret the label, however, is the first step. Basically, it is sufficient to verify that the level of Nitrogen (indicated with the initials “N”) is considerably lower than that of the other two macro-elements that make up all fertilizers for plants, namely Phosphorus (indicated with the letter “P”) and Potassium (“K”). As an indication, a good fertilizer for cacti and succulents should have 1 part Nitrogen, 2 or 3 parts Phosphorus and 4 or 6 parts Potassium. The dosages indicated by the various manufacturers are variable, but it will be enough to keep these proportions in mind to choose the correct product. According to the most commonly used formulations, we can have a ratio of 6-18-36, or 5-15-30, where 5 stands for the Nitrogen dosage, 15 for the Phosphorus one and 30 for the Potassium one. Balanced fertilizers are to be avoided, those with equivalent dosages of the three macroelements (for example, 10-10-10). In addition to the three macroelements, a good fertilizer for succulents should not lack the so-called mesoelements and microelements, such as calcium, magnesium, sulfur, manganese, boron, copper, zinc, iron, which contribute to a balanced development of the plant in various aspects: root system, stems, thorns, flowering, disease resistance.

For the dosage, it will be sufficient to refer to the indications on the package, taking care to halve the quantities in order not to overdo the fertilization, since succulents are extremely adaptable plants with few needs in terms of nutrients, many of which are already present in the growing medium.

If you want to learn more about fertilization, you can read this specific article.

Don’t be in a hurry

In closing, by my experience and the constant contacts I have with readers and enthusiasts who ask me for advice, I would like to reiterate the concept expressed at the beginning of this article: with cacti and succulents, don’t be in a hurry, never anxious. Our plants are more robust and tolerant than we think: let’s make their time our own and not let ourselves be led by the frenzy of wanting to give them excessive attention. Let’s limit ourselves to the correct care and respect their times, which are decidedly less hectic and anxious than ours, remembering that the border between passion and obsession can be thin…

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Here is a video of me moving some of my plants outside my greenhouse:

Correlated articles

How to repot cacti and succulent plants
Substrates for cacti and succulents
The correct soil: the materials you can use

© The texts, videos, photos and graphic elaborations of the site “Il fiore tra le spine” are original material and are covered by copyright. It’s forbidden to reproduce them in any way.

L'articolo Preparing cacti and succulents for spring: exposure, fertilizing, here’s what to do proviene da Il fiore tra le spine.

When they say that a picture is better than words. In this case, there are three photos, but the concept doesn’t change, and the difference between a cactus grown in a “natural” (or “wild”) way and one with a “garden-style”, based on basic notions and beliefs is quite evident. The plants I’m writing about are Ferocactus latispinus obtained from a 2012 sowing of mine. From that same planting, I’ve got at least forty plants. Over the years, I have given away some of them, but most are still with me and are growing beautifully. It’s important to point out that these are plants born from seeds contained in a single fruit (gift of a dear friend), sown the same day and grown over the years in the same conditions, i.e. in my greenhouse, in standard soil (pumice, lapilli and peat in equal parts), watered and fertilized with the same frequency. This is to say that the starting conditions, including the genetics and the grower’s hand, are the same. And yet, as you can see from the photo above, where the three plants (three at random of the twenty-five or so that I have kept for myself) are side by side, they show remarkable differences, at least to the discerning eye and the grower with a minimum of experience.

So let’s see, in this article, how and why different cultivation regimens, assumed as a whole and not just limited to the soil, affect so much the final result and really make the difference between a cactus grown and cultivated in any garden or generic nursery and a cactus grown by an enthusiast or an expert. (…)

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L'articolo How a cactus changes depending on the type of cultivation: the difference made by soil and exposure proviene da Il fiore tra le spine.

Temperatures are still above the seasonal averages, but summer has faded and autumn is on its way. Like every year, at the end of September I started preparing my greenhouse for the cold months. Nothing major, just some cleaning work, moving plants from outside to inside, a check on the heating system and two coats of copper oxychloride on plants a preventive measure. The plants themselves will do the rest, dehydrating following the suspension of watering from mid-September (from now on I will water just a few leafy succulents and, sporadically, Copiapoa and Eriosyce until the end of October) and starting to produce their natural “antifreeze” within the plant tissue of stems.

This is a good time to check the state of health of the plants and, in my case, to “draw some sums” on the results of the Spartan cultivation to which I subjected several specimens, as I explain in the following article. (…)

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L'articolo Spartan cultivation in full sun, and the results can be seen: healthy plants and robust thorns proviene da Il fiore tra le spine.

In the following article, we will see in detail what consists of prevention; which are the pests and diseases that can affect cacti and succulents; such as the symptoms of their action on plants, and how to carry out treatment and care in case of problems. (…)

The importance of air recirculation

The keyword for prevention is air. Air, air and more air. Therefore, airing the environments in which we keep our plants and, consequently, keep humidity rates low. Open greenhouses as much as possible throughout the period from spring to autumn, fans for air recirculation, outdoor cultivation, are all important factors to give our plants the right amount of air. Also, of course, to the use of correct substrates, draining and low humidity, plenty of light and the right fertilization regimes (an excess of nitrogen, for example, forces the growth of succulents and makes them weaker in the face of adversities), proper irrigation and, more generally, cleaning (of soil, pots, tools and instruments, etc.).

Check the plants

A good practice consists, first of all, in observing the plants carefully before their purchase, discarding those suffering, clearly attacked by parasites (such as cochineal, easily recognizable by the naked eye) or deformed at the apex due to the attack of some aphids. Once purchased the plant, it is good to flake it and thoroughly clean the roots (especially if the plant is in peat), checking the condition carefully and repot in suitable soil. Another useful trick is to immediately isolate the plant or plants that we observe in distress or on which we detect the presence of mites (for example the red spider, see below) or parasites such as cochineal. Even more important is to isolate from other plants those subject to fungal attacks: the spores can quickly pass from one specimen to another and cause real disasters. All plants, then, must periodically be checked carefully to identify any problems and isolate the affected specimens to treat them with specific products and avoid that fungi and parasites may affect other plants.

Preventive treatments

Preventive treatments can be useful against fungi and parasites, especially in two specific moments: in autumn and just before the beginning of spring. It is at these times of the year, in fact, that the combination of ambient temperature and humidity, in addition to the low activity of the plants, can favour conditions suitable for the proliferation of mites and bacteria. Before the plants go into stasis, at the end of summer/early autumn, two nebulisations at a distance of 15 days from each other with water and copper oxychloride, possibly combined with sulfur, will protect plants from some types of fungi and bacteria during the winter. In the same way, a couple of nebulisations at the beginning of spring, before watering, will contribute to the prevention at a time when temperatures tend to rise and, with them, the humidity rate due to the March/April rains. Against bacteria in the soil and root parasites, it is possible to carry out systemic treatments, i.e. special products mixed with watering water. Even in these cases, a treatment at the end of summer and one in spring, with the first watering, can be useful for preventive purposes. In these cases, it is possible to use systemic fungicides against radical rot (Previcur can be used against collar rot, while Tebuconazole can be used against fusarium and Propamocarb can be used for a wider spectrum defence). If the fusarium has already attacked the plant, it is advisable to throw away everything: plant, pot and earth.

An excellent choice, respectful of the environment and our health, is to focus on products with low environmental impact, like Neem oil, useful against infestations by mites and parasites. Always remember that chemicals, whether pesticides or fungicides, should be treated with great caution, wearing gloves and masks, as they can be harmful to health if inhaled or in contact with skin (in fact the use of many products is regulated by law and for the purchase and use of some of them, specific patents are required). An interesting alternative to chemicals against insects and pests can be to use natural remedies based on garlic and tobacco.

Some treatment, always for preventive purposes, can be done by nebulization or by the systemic way (i.e. through watering, so that the plant absorbs the product, which will go from roots to stem) even during the growing season. However, if the plants are healthy and robust, the treatments at the end of summer and the end of winter will be enough and the plants will become stronger and will be able to face and solve any problems.

Plant parasites

Plants can be attacked by plant parasites or pests. The first group includes fungi, bacteria, viruses and microplasmas. Fungi and bacteria, in particular, proliferate in the soil in conditions of heat and prolonged humidity. These are, probably, the most insidious and difficult adversities to face. This happens mainly because the presence of plant parasites is manifested only through the symptoms of the disease that they cause to the plant. In other words, fungi, viruses and bacteria cannot be seen with the naked eye, but you can see the effect of their harmful action. Unfortunately, when we realise it, it is almost always too late to save the plant.

 Fusarium  – It is the case, for example, of Fusariosis, caused by Fusarium oxysporum, a fungus present in the soil that causes withering, dry rot and the rapid decay of the plant, which first slows down the vegetation and then stains and then literally withers and dies. In the acute form, the Fusarium causes the basal rot of the affected subject, while in the slow form it causes a chronic infection that causes secretion and suberification of the plant, which slowly dies. Against this pathology, there is usually little or nothing to do, except try to deal with specific systemic fungicides (based on the above-mentioned Tebuconazole, for example). Of fundamental importance is to move the affected plant away from the others and, in case it is too late to save it, throw away plant, soil and pot (unless you want to disinfect it with bleach).

 Root and collar rots  – They are caused by fungi in persistent hot/damp conditions and by water stagnations in the soil. They affect the roots of the plants and extend to the collar causing their rot and, consequently, the death of the plant. If taken in time, for example after having noticed a slowing in the growth of the plant and its deterioration, you can intervene by flaking the specimen, removing all the old soil and cutting off all the rotten roots and then let the plant dry for at least a couple of weeks in the air but not in the sun. If the rot has hit the collar, you can try a rescue by cutting the plant to the healthy part (i.e. until the pulp is white and has no dots or brown areas). It is essential to use a sharp cutter by disinfecting the blade with alcohol before each cut, to avoid infecting the healthy part. Also in this case, after this operation, you will have to leave the plant in a shaded but very ventilated place for some weeks, until the cut part is completely dry and scarred. At that point, you can place the plant on pumice to try to promote the rooting of the cutting.

 Pythium  – It is a fungus that attacks the seedlings bringing the roots and the collar to rot. If it is not too late to intervene, the plants should be flared, the old soil removed and the seedlings left to dry. Afterwards, it is possible to use a fungicide based on Previcur, both for preventive and curative purposes.

 Powdery mildew  – This is another pathology caused by fungi, commonly called powdery mildew. It develops in conditions of low humidity and temperatures above 20 degrees and spreads through the spores carried by the wind. It reveals with white/greyish pulverulent spots, which lead to the decay of the plant. Against powdery mildew can be useful nebulizations with water mixed with sulfur.

 Sooty Mould  – Also the sooty mould is caused by fungi, a pathology that leads to the production of a dark-coloured crust or to the formation of black powder, often on cacti areoles, at the base of thorns. Are affected by it some cacti, like Ferocactus, which produce honeydew, nectar secreted by the areoles. In case of smoke, it is possible to intervene with copper sulfur, either by spraying or manually, by cleaning the affected areas with a toothbrush or a cotton bud soaked in a solution based on water, sulphur and copper.

 Rust  – This name indicates a pathology, septoria, caused by a fungus called septoria. The symptoms are yellowish spots on the stem, more or less extended depending on the severity of the attack. They are created in conditions of poor ventilation and stagnant humidity. The rust seems to particularly affect Ferocactus latispinus during the winter. It can be controlled by providing the plants with maximum ventilation and low humidity. In case of attack it is good to move the affected plants, give them more air and intervene with copper-based products.

 Botrytis  – Botrytis cinerea, also known as “grey mould”, is caused by a fungus in conditions of persistent humidity and poor aeration. It creates spots initially dark green with yellowish edges. Then the spots are darker until they become brown or black and are covered with grey mould. The best prevention is a good recirculation of air and space between one plant and another. In case of an attack by botrytis, it can intervene with systemic fungicides in association with copper oxychloride. Isolate the affected plant immediately to prevent the spores from passing on to other specimens.

Animal parasites

Even against animal parasites, the best weapon remains prevention, understood as proper cultivation aimed at obtaining robust and healthy specimens. However, some bad encounters between our plants and some parasites (or lice, as they are commonly called) can always happen.

 Cochineal  – These insects are among the main enemies of succulent. They attack plants like the Opuntia, but they do not disdain the other Cactaceae. They can be of three types: waxy cochineal, mealybugs and shield. They usually strike the apex of the plants, but they can nest, also between the roots when the soil remains dry for long periods. In the latter case, the attack is more dangerous, because we only notice it when we repot or if we are very careful if we see that the plant has blocked the growth and is declining without any other apparent causes. The mealybugs suck the sap from the succulents, weakening them, and compromising their growth. The waxy cochineal nestles between the coasts of the Cactaceae or around the areoles, is a couple of millimetres long and secretes a layer of wax. The cotton cochineal, as its name says, produces small white woolly balls. It threatens the apex of the cacti or between the leaves of the succulents and sucks the sap. If the infestation is limited, you can manually remove the mealybugs or crush them with a toothpick. In the case of root cochineal, it is necessary to remove the soil, clean the roots thoroughly, shorten them and, immerse the root system or the whole plant for a few minutes in a contact insecticide and then let to dry for a few days before repotting in the new soil. The cochineal shield is more difficult to remove manually, which also reproduces quickly and, if left to do, can literally cover the plant seriously compromising its growth until it decays. It clings tenaciously to the trunk of the cacti, is white/greyish and has the typical shield shape. They can be removed with a toothbrush, or removed with a nail, but it is not always an easy action. Specific systemic insecticides, or summer mineral oil, can be used against mealybugs. It is also useful alcohol (diluted in water and nebulized), which dissolves the waxy protection produced by these insects and makes them more vulnerable to a subsequent treatment based on specific products. In case of radical cochineal, it is good to immerse the roots (or the entire plant) for a few minutes in a solution based on water and specific anti-cochineal products. When crushed, the cotton cochineals produce a red substance that was used as a textiles dye by Mexican populations.

 Red spider  – This is a small phytophagous mite (Tetranychus urticae), not visible to the naked eye. It proliferates in dry, warm conditions, so it can develop in the hot season if the waterings are very spaced, and the climate is particularly dry. It strikes the apex of the cacti, where the tissues are more tender, and causes secretion on the epidermis which assumes a grey/reddish colour. Growing up, the stem is chapped and aesthetically compromised. At the same time, a massive attack by the red spider can slow the growth of the plant and compromise its proper development. Good prevention against these mites consists in the cultivation of cacti in full sun so that the epidermis hardens and is less subject to the attack of the red spider. At the same time, outdoor cultivation encourages the presence of insects competitors able to contain the development of this mite. A red spider infestation can be countered by systemic and acaricide insecticides such as kelthane, dicofol and sulfur products. It is important not to use the same active ingredient often because the red spider quickly develops acaricide-resistant strains.

 Nematodes  – They look like little worms. They develop in fresh and humid soils and can penetrate inside the roots of the plants blocking the lymphatic flow and leading the plant to growth block, decay and death. They can be easily noticed only in case of repotting: the roots have swellings, nodules a few millimetres in size. As a preventive measure, it is advisable to take a good look at the roots of freshly purchased plants or during each repotting. In the presence of nematodes it is necessary to cut the roots as much as possible and throw the pot and all the old potting soil. Some growers recommend soaking the roots for about twenty minutes in water at 50°. When you notice the presence of these nematodes, often it is too late because they move from one root to another and eradicating them is quite difficult. It is not by chance that several experts advise throwing away the plant in case of an attack by nematodes.

 Aphids  – Fortunately, they do not frequently attack succulents. These are green or black insects that can weaken the affected plants by opening the door to viruses. Specific products (such as Movento) are easily found against aphids, although they can be removed with soapy water (for example, using a Marseille soap diluted in water).

 Metcalfa  – They are small white or pale green insects and appear from the middle of May. They suck the sap of the plants and can facilitate the onset of honeydew and soot. They can be counteracted with specific insecticides, such as those used against cochineal.

 Thrips  – They are very small so that it is almost impossible to see them with the naked eye. They usually attack the flowers, attracted by the pollen, causing dryness, malformation to the petals and favouring the attack by viruses. Against these insects, you can use blue chromotropic traps, or Marseille soap and water or specific insecticides (dimethoate).

 Swarming Fly  – The larvae of these Dipterans are dangerous for seedlings. In fact, they nest in the soil and attack the collar and the roots of the young plants, causing their decay and subsequently their death. The swarming fly is attracted by humid soils rich of organic substance (e.g. peat); for this reason, it can easily attack the seeds, which for the first months must have the soil always humid. The larvae of swarming fly are fought with specific insecticides to be administered together with the waterings.

 Snails and ants  – Among the potential enemies of cacti and succulents there are also snails and ants. Snails can cause considerable damage because they eat the fleshy leaves of succulents and can attack the apical part of cacti, which is more tender. When they are found, they must be immediately removed from the plants, whilst to keep them away, we can resort to the old system of the saucer with some beer, which attracts them and the stuns. There are also specific products in granules to be spread on the surface of the substrate: for snails, they are toxic and eliminate the problem before the molluscs attack the plants.
Ants are not dangerous, but they steal the seeds of succulents and are attracted to the nectar that the glands of some cacti produce (e.g., Ferocactus). They can also carry insect eggs that are harmful to plants. They contrast with specific insecticides, often powdered, to be spread around pots to keep them away.

Wondering what is the right soil for cacti and succulent plants? You can read here…

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How to repot cacti and succulent plants
Substrates for cacti and succulents
The correct soil: the materials you can use

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L'articolo Diseases and pests of cactus and succulents: how to recognize them and how to prevent their attacks proviene da Il fiore tra le spine.

Light is fundamental for every living being, starting with plants. This is obvious, but we cannot ignore it if we want to grow cacti and succulent plants in general. Plants, moreover, that often need many hours of light per day; in some cases direct or non-filtered light, in others not straight but equally intense daylight. In fact, there are succulent plants that, if placed in full sun, slow down growth, burn and even die. On the contrary, many succulent plants and many cacti, if they do not receive the right amount of direct light, will have stunted growth, with weak thorns and elongated stems.

In this article, we see what we need to know about the right exposure of cacti and succulent plants in general. Also, at the end of this article, you find a table summarizing the type of exposure needed by the main families of succulents. (…)

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L'articolo How much light do cactus need to grow well? The importance of sun and air and a summary table proviene da Il fiore tra le spine.

Do cacti resist frost? In winter, do succulent plants have to be kept indoors or can they stay outside? And what are the minimum winter temperatures they can tolerate? Even among experienced growers, the minimum temperatures of cacti and succulents are still debated today. I tackle the topic starting, as always, from my personal experience, which is my only way to have accurate data, found in the field, related to my system and my growing conditions, here in North of Italy. Let’s say right away that during winter I keep most of my plants in the greenhouse. It is a large greenhouse of 60 square meters and with a height, at the top, of 4 meters. These dimensions guarantee a satisfying volume of air, which in turn prevents moisture stagnation, the first real enemy of cacti and succulent plants in winter.

Let’s see, in the following article, the various factors that influence the resistance of cacti and succulents to cold. At the end of the article, you will also find a schedule with the minimum temperatures tolerated by the various families of succulents. (…)

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L'articolo Succulents and cold: how to care for cactus in winter and the minimum temperatures tolerated proviene da Il fiore tra le spine.